Liquid cooled cylinder sleeve, particularly for internal combustion engines

ABSTRACT

Cooling tubes, preferably semicircular, and matching in the aggregate approximately the contour of the cylinder sleeve (13), are cast into the sleeve; the tubes (16) are formed with radially extending connecting stubs and with locating means to place them close to the inner wall surface of the liner, and in a region free from axial stresses imposed on the complete cylinder linertube casting. Preferably, a group of superimposed tubes are used, interconnected by short riser tubelets. The semi-circular tube sections can have connecting stubs, plugged during casting and, if desired, remaining plugged, extend at the diametrical region of the separation of mold sections used to cast the cylinder sleeve.

I United States Patent [151 3,659,569

Mayer et al. [4 1 May 2, 1972 54] LIQUID COOLED CYLINDER SLEEVE, 1,968,449 7/1934 I-Iefti ..123/44.83 x

PARTICULARLY FOR INTERNAL 2,331,554 10/1943 Irgens COMBUSTION ENGINES 2,252,961 8/1941 Campbell...

2,277,113 3/1942 Klmmel ..92/144 X [72] Inventors: Stephan Mayer; Rolf Engel, both of Augsburg, Germany FOREIGN PATENTS OR APPLICATIONS [73] Assignee: Maschinenlabrik Augshurg-Nurnberg AG, 577,185 5/ 1933 Germany ..123/41.8 Augsburg, Germany 224,540 5/1925 Great Britain ..l23/41.84

[22] Filed: 1970 Primary Examiner-Al Lawrence Smith [21] Appl. No.: 86,179 Altorney-Bauer&Goodman A [30] Foreign Application Priority Data [57] ABSTR CT Cooling tubes, preferably semicircular, and matching in the Nov. 3, 1969 Germany ..P 19 55 140.7 aggregamappmximately the contour of the cylinder Sleeve (13), are cast into the sleeve; the tubes (16) are formed with [52] CL "123/ 41:79 123/ radially extending connecting stubs and with locating means [51] Int Cl F02 1/10 14 to place them close to the inner wall surface of the liner, and l 58] Fie'ld 44 8 4481 44 in a region free from axial stresses imposed on the complete 173/44 83 R 5 5 7 6 cylinder liner-tube casting. Preferably, a group of superim- Ur Isa/334 posed tubes are used, interconnected by short riser tubelets. The semi-circular tube sections can have connecting stubs, 56] References Cited plugged during casting and, if desired, remaining plugged, extend at the diametrical region of the separation of mold sec- UNl STATES PATENTS tions used to cast the cylinder sleeve.

1,260,861 3/1918 Bie ..92/171 X 11 Claims, 4 Drawing Figures Patented May 2, 1972 nun QRQ LIQUID COOLED CYLINDER SLEEVE, PARTICULARLY FOR INTERNAL COMBUSTION ENGINES The present invention relates to liquid cooled cylinder sleeves, particularly for internal combustion engines of high power.

High-power internal combustion engines operate with high temperatures in the combustion chamber. Cooling of the cylinder, and particularly of the upper portion of the cylinder adjacent the combustion chamber is thus of substantial importance. The cylinder, usually formed as a cylinder sleeve is subjected to substantial forces. During combustion, there are substantial gas pressures acting radially with respect to the cylinder. To hold the cylinder assembly together, and particularly to secure the cylinder head, the radially extending upper or head portion of the cylinder sleeve is subjected to substantial axial pressures. For this reason, the design of the cylinder sleeve, and particularly its upper or head portion is difflcult and frequently requires a substantial amount of material, particularly with respect to the remainder of the cylinder sleeve. The amount of material used for the cylinder sleeve head requires special cooling to prevent excessive heating, which, due to uncontrollable expansion may cause dangerous warping of the upper cylinder surfaces. The inner wall of the cylinder is particularly subjected to heat stresses, which may even cause cracks and fissures to appear. Insufficient removal of heat additionally interferes with proper lubrication and the formation of a suitable film of lubricant between the piston rings and the inner wall of the cylinder, which may lead to scoring, or even seizing of the interior surface of the cylinder.

It has previously been proposed to cool the cylinder sleeve, and particularly the head portion thereof, by providing a cooling channel directly therein. Cooling fluid can flow in a complete, interiorly closed ring duct, cast into the cylinder sleeve (see French Pat. No. 588,551); in another construction, ring-shaped grooves in interconnection with the outer portion of the cylinder sleeves have been proposed (see Swiss Pat. N 0. 73495). Cooling arrangements of the described type cause mechanical weakening of the upper cylinder sleeve portion. If a ring-shaped groove, open to the outside, is provided in the upper portion of the cylinder liner, axially transferred stresses due to the screw-connection of the cylinder head may cause application of bending stresses to the cylinder head, which may result in undesirable bulging of the interior wall of the cylinder sleeve. The cooling effect of a duct, cast into the cylinder sleeve itself is difficult to control, since the distance of the duct from the interior wall of the cylinder cannot be accurately predetermined.

It is an object of the present invention to provide a cylinder sleeve, and particularly a construction for the upper portion of a cylinder sleeve in which the interior wall portion can be effectively cooled, and which is so constructed that stresses in assembly, or during operation do not interfere with the mechanical strength of the cylinder sleeve, or cause dangerous deformations thereof.

SUBJECT MATTER OF THE PRESENT INVENTION Briefly, at least one cooling tube, and preferably a plurality of cooling tubes arranged in semicircular assemblies and matching the curvature of the cylinder sleeve itself are cast into the head portion of the sleeve; the tubes are formed with radially extending connecting stubs which serve simultaneously as a locating means before and during casting, and, if desired, to conduct cooling fluid into and away from the tubes. The tubes themselves are placed close to the inner wall of the sleeve and in a region free from axial stresses imposed on its radially extending head portion upon assembly of the cylinder sleeve to a complete engine cylinder.

A plurality of superimposed, preferably interconnected semi-circular tube sections are placed, prior to casting, into the mold in such a manner that the connecting stubs extend radially approximately in the region of the junction of a pair of mold halves; the outer ends of the radially extending stubs are then plugged, and the cylinder liner can be cast. Upon removal of the halves, some of the plugs may remain, if interconnecting tublets have been provided to form a complete, closed cooling fluid circuit; or, selected plugs can be removed and connected to a source and a drain for cooling fluid. The tubes themselves preferably are flattened at the outer surface to have an essentially oval cross section with the longitudinal axis of the oval extending parallel to the axis of the cylinder sleeve itself.

The invention will be described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 is a longitudinal cross-sectional view through the upper portion of a cylinder for an internal combustion engine along lines I-I of FIG. 2;

FIG. 2 is a transverse sectional view along lines 11-11 of FIG. 1;

FIG. 3 is a fragmentary view to a greatly enlarged scale of the encircles portion of FIG. 1; and

FIG. 4 is a schematic representation of the cooling fluid circuit of one half of the cooling system, prior to being cast.

FIG. 1 illustrates a cylinder head 11, connected by means of cylinder head bolts (not shown) in known manner to a cylinder block 15. The gap between the cylinder head 11 and block 15 is bridged by a cylinder sleeve 13 encircled by a sleeve head 12. Cylinder sleeve 13 encloses the combustion chamber 14.

The transverse sectional view of FIG. 2 illustrates the cylinder sleeve head 12 and shows a system of cooling tubes 16, closed in themselves, and cast into the mold, separated into twohalves in dotted line B-B. The cooling tubes 16 are located by bending the tubes in the region of the junction line B-B into radially extending stubs 16'. The stubs are closed off by means of plugs 17, and the end stubs are held by locating sleeves or elements 18 within the casting mold. Thus, the cooling tubes 16 are well and securely located and their distance a from the inner wall of the cylinder sleeve 13 can be accurately and uniformly maintained. An entire array of cooling tubes, superimposed one above each other is interconnected by means of tubelets 19 (FIG. 3, 4) to provide a closed cooling fluid circuit.

The tubes 16 are preferably flattened into oval cross section, with the major axis of the oval extending approximately parallel to the inner wall of the cylinder sleeve. Thus, uniform and good cooling is obtained, and the outer zones of the cylinder sleeve head 12 are thermally shielded. The shape of the cylinder sleeve head 12, mechanically supporting the inner wall of cylinder sleeve 13 provides excellent support against stresses due to radial gas pressure within combustion chamber 14. The cylinder sleeve head has essentially vertically extending rectangular cross section. Axially extending stresses due to interconnection of the cylinder head 11 with the cylinder block 15 only stress the outer regions of the cylinder sleeve head 12 and are directly transmitted to a suitable bearing surface on the cylinder block. The cylinder sleeve head 12 is located with respect to the cylinder head by means of a groove or notch 20, matching a locating ring on the cylinder head 1 l.

The comparative heavy outer region of the cylinder sleeve head 12 provides a wide mouth when the cylinder sleeve is cast, so that cylinder sleeve material can readily flow to the lower regions of the cylinder sleeve 13, so that in foundry operations it is not subjected to blow holes or similar casting defects.

FIG. 4 illustrates a subassembly of cooling tubes 16, each in approximately semi-circular form and matching the curvature of the inner wall of the cylinder sleeve 13. The sub-assembly is secured in the casting mold at the various radially extending stubs 16'. Cooling liquid is introduced by means of a supply duct 21, passing through the lowermost cooling tube 16 (which is plugged by means of plugs 17 at both ends) then passes by means of a riser tubelet 19 from the other end to the next adjacent tube 16, where the cooling fluid will again pass back to the first end, rise to the next higher one, and so on. The last end of the uppermost cooling tube 16 is left open and connected to a drain or cooling fluid outlet, or conducted to the remaining cooling fluid circuit of the engine, for example to the cylinder head 11. Various tubes can be selectively pluggedto connected to the cooling fluid circuit as desired.

Forming the cooling tubes in a pair of essentially semi-circular assemblies has the advantage that the sub-assemblies can be moved, independently of each other, and adjusted with respect to the inner surface of the cylinder sleeve. Individual adjustment, and location of the semi-circular sub-assemblies substantially simplifies their accurate positioning, and effectively prevents damage or dislocation of the cooling tubes with respect to the casting mold upon insertion of the heavy and unhandy core, necessary for casting, to form the combustion chamber 14. The sub-assemblies of semi-circular, interconnected tubes can be made entirely independently from the casting of the cylinder sleeve, and provided with suitable holding and locating means for ease of assembly with the casting mold. The flattened tubes can be brought, with low tolerances, close to the inner wall of the cylinder to efi'ect excellent cooling of the inner walls of the sleeve while thermally separating the sleeve and the outer zone of the sleeve head portion. The amount and cost of material required for the cooling arrangement in the head portion of the cylindersleeve is low, and manufacture thereof by partial bench sub-assembly and subsequent casting-in of the sub-assembly'into the sleeve head, is facilitated.

The present invention has been illustrated and described specifically in connection with cylinder sleeves for internal combustion engines; various changes and modifications may be made as required by the design of the engine with which the cylinder sleeve is to be used. The shape, the number of outlets, and the angular span of the tubes 16, for example, can all be varied to suit design requirements.

We claim 1. Liquid cooled cylinder sleeve construction comprising a cylinder sleeve (13), a radially extending cylinder sleeve head portion (12) and at least one cooling tube (16) matching the curvature of the cylinder sleeve, cast into the head portion (12) of said cylinder sleeve, and formed with at least one radially extending connecting stub (16'), said tube 16) being placed close to the inner wall of said sleeve (13) and in a region free from axial stress imposed on its radially extending head portion (12) when assembled to a cylinder.

2. Cylinder sleeve construction according to claim 1 including locating means (18) operatively associated with said stubs l6) and locating said stubs within said sleeve.

3. Cylinder sleeve construction according to claim 1 wherein said tubes (16) are longitudinally flattened with their major axes extending essentially parallel to the axis of the sleeve (13).

4. Cylinder sleeve construction according to claim 1 wherein said tubes extend essentially semi-circularly around the inner wall of said sleeve, and said connecting stubs (16') extend diametrically opposite from the ends of each semi-circularly extending tube.

5. Cylinder sleeve construction according to claim 4 wherein the sleeve is enclosed by a sleeve head formed in two semi-circular sections;

and wherein said stub (16) extending from said semi-circularly extending tubes (16) are located adjacent the junction (B-B) of the sections forming the sleeve head.

6. Cylinder sleeve construction according to claim 1 wherein a plurality of superposed tubes (16) are cast into said cylinder sleeve;

and verticallyinterconnecting tube elements (19) are provided interconnecting superposed tubes to provide a closed cooling fluid path through said plurality of tubes.

7. Cylinder sleeve construction according to claim 6 wherein said plurality o cooling tubes (16) and said interconnecting tube elements (19) form a sub-assembly cast into said sleeve as a unit.

8. Cylinder sleeve construction according to claim 7 wherein said tubes extend essentially semi-circularly;

and a pair of sub-assemblies of superposed tubes, each subassembly having separately interconnected tubes, are provided, located around the circumference of the inner wall of said sleeve;

a lower, and a higher tube, each, being adapted for connection to supply (21) and removal duct means for connection of cooling fluid to the tubes of the sub-assemblies.

9. Cylinder sleeve construction according to claim 7 wherein all tubes are similar;

and plug means (17) are located close to the upper stubs of those tubes not'connected to a supply, or removal duct.

10. Cylinder sleeve construction according to claim 1 wherein said tubes are discrete, structural elements separate from said sleeve, and cast therein.

11. Cylinder sleeve construction according to claim 1 wherein said sleeve has a head portion (13) formed with a locating means to locate said sleeve within a cylinder, thus separating an outer zone subject to axial compression from an inner zone;

and said tubes are located in a region of said sleeve which.

in axial projection, falls in said inner zone. 

1. Liquid cooled cylinder sleeve construction comprising a cylinder sleeve (13), a radially extending cylinder sleeve head portion (12) and at least one cooling tube (16) matching the curvature of the cylinder slEeve, cast into the head portion (12) of said cylinder sleeve, and formed with at least one radially extending connecting stub (16''), said tube (16) being placed close to the inner wall of said sleeve (13) and in a region free from axial stress imposed on its radially extending head portion (12) when assembled to a cylinder.
 2. Cylinder sleeve construction according to claim 1 including locating means (18) operatively associated with said stubs (16'') and locating said stubs within said sleeve.
 3. Cylinder sleeve construction according to claim 1 wherein said tubes (16) are longitudinally flattened with their major axes extending essentially parallel to the axis of the sleeve (13).
 4. Cylinder sleeve construction according to claim 1 wherein said tubes extend essentially semi-circularly around the inner wall of said sleeve, and said connecting stubs (16'') extend diametrically opposite from the ends of each semi-circularly extending tube.
 5. Cylinder sleeve construction according to claim 4 wherein the sleeve is enclosed by a sleeve head formed in two semi-circular sections; and wherein said stub (16'') extending from said semi-circularly extending tubes (16) are located adjacent the junction (B-B) of the sections forming the sleeve head.
 6. Cylinder sleeve construction according to claim 1 wherein a plurality of superposed tubes (16) are cast into said cylinder sleeve; and vertically interconnecting tube elements (19) are provided interconnecting superposed tubes to provide a closed cooling fluid path through said plurality of tubes.
 7. Cylinder sleeve construction according to claim 6 wherein said plurality o cooling tubes (16) and said interconnecting tube elements (19) form a sub-assembly cast into said sleeve as a unit.
 8. Cylinder sleeve construction according to claim 7 wherein said tubes extend essentially semi-circularly; and a pair of sub-assemblies of superposed tubes, each sub-assembly having separately interconnected tubes, are provided, located around the circumference of the inner wall of said sleeve; a lower, and a higher tube, each, being adapted for connection to supply (21) and removal duct means for connection of cooling fluid to the tubes of the sub-assemblies.
 9. Cylinder sleeve construction according to claim 7 wherein all tubes are similar; and plug means (17) are located close to the upper stubs of those tubes not connected to a supply, or removal duct.
 10. Cylinder sleeve construction according to claim 1 wherein said tubes are discrete, structural elements separate from said sleeve, and cast therein.
 11. Cylinder sleeve construction according to claim 1 wherein said sleeve has a head portion (13) formed with a locating means to locate said sleeve within a cylinder, thus separating an outer zone subject to axial compression from an inner zone; and said tubes are located in a region of said sleeve which, in axial projection, falls in said inner zone. 